Subject:
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adding a third serial port
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Newsgroups:
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lugnet.robotics.handyboard
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Date:
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Tue, 23 Apr 1996 23:33:52 GMT
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Original-From:
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Randy Sargent <RSARGENT@NEWTONLABS.COMstopspam>
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Viewed:
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1651 times
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> ... I've got two devices, my mouse and my internal modem, which are
> always connected at the same time. What does this mean? It means that IRQ
> 3 and 4 are both always in use. The problem arises when I try to use my
> _external_ COM port, COM3. Simply, it doesn't work, because the IRQ it
> needs is already in use by either the modem or my mouse. This is no doubt
> a _really annoying problem._
I agree that this is a most annoying problem. On the other hand, other
types of computers get away from this problem by not being so expandable.
Some day, when "plug and play" actually is implemented by most of the
hardware vendors, some of these PC-specific hardware configuration problems
will hopefully go away.
You need to do two things to figure out which IRQ to use:
* The first is to figure out which interrupts your serial board can
support, in addition to IRQ's 3 and 4, for your COM3 port.
* The second is to find out from Windows 95 which IRQs are already in use.
The only way I know to do it is somewhat time consuming. Go to "Start" ->
"Settings..." -> "Control Panels" -> "System" -> "Device Manager". Then,
expand each device category, and double click on each device in
succession. For devices which have a "Resources" section, record on a
sheet of paper which IRQ(s), if any, are used. Many devices don't have a
resources section; these won't use any IRQs. You might want to write down
the IO ports in use as well; this won't help you for your serial ports,
but might help down the road if you install additional boards, such as an
ethernet board or a sound blaster.
Assuming you can find an unused IRQ your serial board supports, you're
set. Just change the jumpers on the board, and things -should- work. If
Windows 95 doesn't get the port to work still, you might have to set the
IRQ manually in the Device Manager (go to COM3 -> "Resources" and change
the IRQ manually).
Occasionally you won't be able to find a free IRQ your board supports.
Then you have to play musical IRQ's; some of the IRQs from some of your
boards might be able to be changed, to leave a gap for your serial board.
You may be able to change the IRQs of any serial ports on your motherboard
by running "setup" during reboot. Also, different serial boards support
different sets of IRQs. Look especially for the serial boards with the
wider "16-bit" interface (two edge connectors side by side, instead of just
one). These usually have a larger variety of IRQs to use (they just use
the wider connector to get to the additional IRQs; they still only use 8
bits to transfer data).
Good luck.
-- Randy
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